[mpich-discuss] lock/unlock regions and process synchronization

[Alberto Giannetti]

Yes, thanks. I'd like the code for both the poll and hybrid version  
of the algorithm.
Great paper, btw.

Rob.

On Jul 10, 2008, at 5:39 PM, Rajeev Thakur wrote:

> Yes, this paper describes how to implement mutex locks using MPI  
> one-sided
> communication:
> http://www-unix.mcs.anl.gov/~thakur/papers/atomic-mode.pdf . I can  
> send you
> the code if you like.
>
> Rajeev
>
>> -----Original Message-----
>> From: owner-mpich-discuss at mcs.anl.gov
>> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Robert Kubrick
>> Sent: Thursday, July 10, 2008 4:29 PM
>> To: mpich-discuss at mcs.anl.gov
>> Subject: Re: [mpich-discuss] lock/unlock regions and process
>> synchronization
>>
>> I checked the code in the examples, I understand MPI_Accumulate/
>> MPI_Get is the key to achieve read/write atomicity but I actually
>> need to perform a set of operations on the window, including random
>> assignments. Is there a way to simulate a semaphore through MPI-2
>> generalized requests?
>>
>> Rob.
>>
>> On Jul 10, 2008, at 4:53 PM, Rajeev Thakur wrote:
>>
>>> You could use some out-of-band synchronization like that to achieve
>>> atomicity.
>>>
>>> Rajeev
>>>
>>>> -----Original Message-----
>>>> From: owner-mpich-discuss at mcs.anl.gov
>>>> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of
>> Robert Kubrick
>>>> Sent: Thursday, July 10, 2008 3:46 PM
>>>> To: mpich-discuss at mcs.anl.gov
>>>> Subject: Re: [mpich-discuss] lock/unlock regions and process
>>>> synchronization
>>>>
>>>> Thanks Rajeev, I already have the book in the mail. On a related
>>>> note, is there any potential issue using SYSV semaphores with one-
>>>> sided communications? While the active task is completing
>> the set of
>>>> instructions, all the other slave processes could wait on a
>>>> semaphore.
>>>>
>>>> On Jul 10, 2008, at 4:11 PM, Rajeev Thakur wrote:
>>>>
>>>>> What you are trying to do is an atomic read-modify-write,
>>>> which is not
>>>>> trivial to do with the MPI-2 one-sided operations. There
>>>> are two ways
>>>>> described in the book, Using MPI-2. One is easier to understand
>>>>> than the
>>>>> other one, but is less scalable. The source code for both is
>>>>> available in
>>>>> the MPICH2 distribution. See fetchandadd.c and
>> fetchandadd_tree.c in
>>>>> test/mpi/rma.
>>>>>
>>>>> Rajeev
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: owner-mpich-discuss at mcs.anl.gov
>>>>>> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of
>>>> Robert Kubrick
>>>>>> Sent: Thursday, July 10, 2008 3:04 PM
>>>>>> To: mpich-discuss at mcs.anl.gov
>>>>>> Subject: [mpich-discuss] lock/unlock regions and process
>>>>>> synchronization
>>>>>>
>>>>>> I need to access a one-sided window region in a master
>>>> from multiple
>>>>>> slave processes. Each slave needs to read the window
>> contents, then
>>>>>> update the same window area:
>>>>>>
>>>>>> MPI_Win_lock(...);
>>>>>> MPI_Get(&idx, ...);
>>>>>> MPI_Win_unlock(...);
>>>>>>
>>>>>> // Got idx, check value
>>>>>> if( idx > 10 ) {
>>>>>>    idx += 5;
>>>>>>    MPI_Win_lock(...);
>>>>>>    MPI_Put(&idx);
>>>>>>    MPI_Win_unlock(...);
>>>>>> }
>>>>>>
>>>>>> How can I make sure another process does not access 'idx'
>>>>>> between the
>>>>>> two lock/unlock regions in the example?
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>
>>
>